In the world of sewing production and home crafts you can often find markings 40/2 on spools of thread. For a beginner, these numbers may seem like just a set of numbers, but for a professional, this is an exact formula that determines the strength characteristics, thickness and scope of application of the material. Understanding this coding allows you to avoid damage to expensive equipment and get a high-quality seam.
The main confusion arises from the dual designation system that has historically developed in the textile industry. Metric system and system tex often intersect, creating the illusion of complexity where simple logic reigns. In this article we will look at why these parameters are considered the standard for many operations.
You will learn how to select the right needles for a given thread to avoid breaks and skipped stitches. The question of why this particular type of thread has become the “gold standard” for overlockers and coverstitch machines in the mass production of clothing will also be raised.
Decoding the markings: what do the numbers mean?
In order to use the material correctly, you need to clearly understand what is hidden behind the numbers. In the notation 40/2 The first digit (40) indicates the linear density or fineness of an individual thread in the metric number system (Nm). This means that one gram of such thread contains 40 meters of length. The higher this number, the thinner the thread.
The second number (2) indicates the number of warp threads twisted together. So a 40/2 thread consists of two number 40 threads twisted together. This makes it stronger and thicker than a single thread of the same number. Twist in this case plays a critical role, ensuring uniformity and lack of hairiness.
- 🧵 First digit - metric number of thin thread (Nm 40).
- 🔗 Second digit - the number of folds (twists) in the finished thread.
- ⚖️ Final thickness - the result of addition and twist, affecting the patency through the needle.
- 💪 Strength - directly depends on the number of additions (number 2, 3 or 4).
There is a common misconception that 40/2 thread and 20/1 thread are the same thing. Mathematically it is close, but physically the structure is. Twisted threads behave differently when subjected to tension and friction against the needle. That's why confectionery threads always have a composite structure.
⚠️ Attention: Never attempt to insert 40/2 thread into a needle marked #70 or #75. This will lead to constant breaks and damage to the eye of the needle, since the diameter of the thread will be too large for such a hole.
For everyday understanding, you can use the analogy with ropes: if you take two thin ropes and twist them, you get a thicker and stronger cable. It is on this principle that the 40/2 structure is created. This allows manufacturers to vary the properties of the final product by changing the number of folds.
Physical properties and composition of thread 40/2
Most often, the marking 40/2 means polyester (lavsan) threads. Their synthetic origin gives them high tensile strength and excellent wear resistance. They do not rot, are resistant to detergents and retain their color even after many washes.
However, there are also cotton analogues on the market, although they are less common in the industrial segment. 40/2 cotton will have a matte sheen and less elasticity. When choosing a material, it is important to pay attention to twist. A good thread should be tightly twisted so that when passing through the sewing machine it does not fluff up or get stuck in the mechanisms.
The influence of twist on seam quality
If the thread twist is too loose, the seam will look loose and unsightly. If it is too strong, the thread will “live its own life,” twisting into a loop and causing the seam to warp. Optimal twist provides a balance between strength and smoothness through the needle.
Heat resistance is another important parameter. Polyester 40/2 can withstand high sewing speeds without burning out from friction against the needle, which is critical for industrial speeds of 5000-7000 stitches per minute. For home use, this is also a plus, as it reduces the risk of synthetic fabrics melting.
- 🌡️ Heat resistance — withstands heat from friction at high speeds.
- 💧 Moisture resistance — does not absorb water, does not rot, dries quickly.
- 🎨 Color fastness — painted in bulk or superficially with high fixation.
- 🛡️ Chemical inertness - not destroyed by sweat and household chemicals.
It is important to note that the surface of the 40/2 filament is often covered silicone or special wax. This coating facilitates sliding, reduces friction and prevents heating. If you notice that the thread has become rough or fluffy, the protective layer may have been damaged during storage.
Application area: where number 40/2 is used
Thread 40/2 is a universal soldier in sewing. Its main purpose is to sew products from medium-density fabrics. It is the workhorse of sewing shops where speed and reliability are paramount. It is ideal for stitching parts where a strong but not too noticeable seam is required.
In the household, such threads are often used for hemming trousers, repairing clothes and sewing bed linen. They fit well in stitches on fabrics such as calico, satin, thick knitwear and even some types of denim (not too thick). Versatility is the key word here.
Overlockers and coverstitch machines are the element of 40/2 threads. Thanks to their structure, they perfectly form an elastic seam that stretches with the fabric without bursting when worn. Unlike thicker counterparts, they do not create excess volume in the seams, which is important for lightweight clothing.
- 👖 Clothes - blouses, shirts, dresses, light outerwear.
- 🛏️ Home textiles - bed linen, curtains, tablecloths.
- 🧸 Toys — sewing soft toys from medium-fleecy plush.
- 👜 Accessories — shopping bags, cosmetic bags made of thick fabrics.
⚠️ Attention: Do not use 40/2 thread on leather, faux leather, or very heavy denim (12 ounces and above). For such materials, a thread of greater thickness is required (for example, 40/3 or 50/3), otherwise the seam will simply “sink” into the thickness of the material or break under load.
This number is also often used for decorative stitching when a thin, neat line is required. However, for visible decorative seams on jeans, thicker options are often used. The main rule is harmony between the thickness of the thread and the density of the fabric.
Needle Compatibility and Machine Setup
Selecting the right needle is 90% of success when working with 40/2 thread. As already mentioned, a needle that is too thin will result in breaks, and a needle that is too thick will ruin the fabric. The optimal choice for household machines would be needles with the number №80 (EU 12) or №90 (EU 14).
Industrial lockstitch machines that operate at high speeds often use DBx1 needles or similar sharpening systems. It is important to monitor the condition of the point: a dull needle will “chop” the 40/2 thread, causing frizz and tears. Regular needle replacement is a must.
☑️ Checking the machine settings for thread 40/2
Thread tension is the second critical parameter. 40/2 thread requires medium or slightly loose tension. If the tension is too strong, the thread may become deformed or break during sewing. Checking the quality of the seam should be carried out on a fabric sample.
If you see that the bottom thread is pulled to the right side, then the top tension is too loose. If the upper thread pulls the fabric and loops form below, the tension is excessive. Balance achieved by testing on a patch.
Comparison table: 40/2 vs other numbers
To finally understand the place of 40/2 thread in the hierarchy of sewing materials, let’s consider it in comparison with popular analogues. This will help you quickly navigate the store’s assortment and choose exactly what you need for a specific task.
The difference between 40/2 and 40/3, for example, is significant. The three-thread version is much thicker and stronger, but also requires a larger needle. A comparison with 50/2 will show the difference in thinness: 50/2 will be thinner and less noticeable on the fabric, but also less durable.
| Parameter | Thread 40/2 | Thread 40/3 | Thread 50/2 | Thread 60/2 |
|---|---|---|---|---|
| Thickness | Average | Fat | Thin | Very thin |
| Strength | High | Very high | Average | Low |
| Needle (recommended) | №80-90 | №90-100 | №75-80 | №65-75 |
| Application | Clothes, underwear | Jeans, bags | Delicate fabrics, silk | Silk, chiffon |
Thread 40/2 is the “golden mean” between strength and aesthetics. It is thicker than 50/2, which gives a margin of safety, but thinner than 40/3, which allows it to be used on more delicate fabrics.
The table shows that switching to a different number requires reconfiguring the entire sewing process. You can't just replace the spool in your machine without checking the tension and possibly changing the needle. Each thread number is a separate ecosystem of settings.
Common mistakes and storage tips
Even high-quality 40/2 thread can deteriorate if stored incorrectly. Direct sunlight is the main enemy of polyester and cotton. Ultraviolet radiation destroys the fiber structure, making the thread brittle. Store reels in closed drawers or boxes, away from windows.
Humidity is the second enemy. Although polyester does not rot, high humidity can cause mold to appear on the spool (especially if it is cardboard) or a change in the properties of the lubricant on the thread. A dry, cool place is ideal for your sewing arsenal.
- ☀️ Sun protection - store threads in a dark place.
- 💧 Humidity control - Avoid damp basements or bathrooms.
- 🧹 Cleanliness — regularly wipe the shelves from dust so that it does not get into the machine mechanism.
- 📅 Rotation - use old supplies first, although polyester has a virtually unlimited shelf life.
A common mistake is using old, dry thread. If you have had the 40/2 thread for 10 years, be sure to check it for tearing with your hands before using it. If it tears with a crunch and easily, throw it away, it will ruin your nerves and tissue.
⚠️ Attention: Never store threads near heating devices. Constant temperature changes and dry heat can make the thread brittle, leading to massive breakages while sewing.
Following these simple rules will allow you to always have reliable material at hand. 40/2 thread is a fundamental element in any seamstress's arsenal, and handling it correctly will ensure years of quality work.
Tip: Buy special plastic containers for thread with transparent lids. This will protect them from dust and fading, and will also allow you to quickly find the right color without going through the entire drawer.
FAQ: Frequently asked questions
Can I use 40/2 thread for machine embroidery?
Technically it's possible, but it's not the best choice. For machine embroidery, there are special threads (often rayon or polyester with a special sheen and twist) that are marked 40/2, but they differ in the quality of coverage and smoothness. Regular sewing 40/2 may give a less shiny and neat result in embroidery.
What is the difference between 40/2 thread and 40/2 LL?
Abbreviation LL means "Lavsan Light". This indicates the type of polyester fiber. Unspecified 40/2 thread can be made from different types of polyester, but LL is the standard for light to medium weight fabrics. Essentially, this is a clarification of the composition, not the size.
Why does the 40/2 thread keep breaking in my machine?
There may be several reasons: the top tension is too tight, the wrong needle (too small eye), poor quality of the thread itself (uneven twist) or the presence of burrs on the needle and hook. Start by replacing the needle with a new and larger one (for example, #90).
Is 40/2 thread suitable for a Janome or Brother overlocker?
Yes, this is the standard size for most household and industrial overlockers. However, for overlockers, thread is often purchased in large bobbins (cone winding), since the material consumption when processing edges is very high. A 40/2 reel will also work, but it will have to be changed more often.